1. Field of the Invention
The present invention relates to a magnetic chuck, and more particularly, it relates to a magnetic chuck which is suitable for handling a number of electronic components, for example, held by an appropriate holder.
2. Description of the Background Art
FIG. 6 is a principle diagram showing a conventional magnetic chuck 1, which is of interest to the present invention.
In this magnetic chuck 1, a holding plate 3 holds a plurality of permanent magnets 2, which are distributed at regular intervals. A magnetic plate 4 is opposed to the holding plate 3 holding the permanent magnets 2. Magnetic poles 5 and separators 6 are alternately formed in this magnetic plate 4. The magnetic poles 5 are distributed in the magnetic plate 4 at the same intervals as the permanent magnets 2, which are distributed in the holding plate 3. The holding plate 3 is movable in parallel with the magnetic plate 4 along an arrow 7, and can assume states shown on the left and right sides in FIG. 6.
In order to simplify illustration, the following description is made with reference to iron balls 8, which are objects to be chucked by this magnetic chuck 1.
In the state shown on the left side of FIG. 6, the permanent magnets 2 are vertically aligned with the magnetic poles 5 respectively, so that the magnetic plate 4 attracts the iron balls 8. Thus, a chucking operation is achieved.
In the state shown on the right side of FIG. 6, on the other hand, the permanent magnets 2 are vertically aligned with the separators 6 respectively. Therefore, the magnetic plate 4 is subjected to no magnetic attraction exceeding a prescribed level, and the iron balls 8 are downwardly separated from the magnetic plate 4.
In general, the magnetic chuck 1 having the aforementioned principle has been mainly designed for a machine such as a polishing machine, for example, with strong magnetic force. However, such a magnetic chuck 1 has the following disadvantages:
The magnetic force acting through the magnetic plate 4 is switched on/off by movement of the holding plate 3 along the arrow 7, while relatively strong force is required for such movement of the holding plate 3. Therefore, the holding plate 3 must be moved by a lever (not shown) having a magnification function. In general, such a lever must be provided in a state relatively largely projecting from the outline of the magnetic chuck 1. Further, it is not easy to enable remote control of this lever.
While a magnetic chuck using electromagnets is suitable for remote control, residual magnetism remains in off states of the electromagnets, to require an additional release mechanism for chucking lightweight objects.
In any case, conventional magnetic chucks have complicated structures and large outer configurations. Thus, considerably large spaces and carefulness are required in order to assemble the conventional magnetic chucks into various machines.